Thin profile battery with improved separator and gasket construction

ABSTRACT

A button-type battery has an anode, a cathode, and an electrolyte encased with two terminal housing members. The terminal housing members have respective peripheries that are crimped together to form a fluid-tight seal. An insulating gasket is provided between the peripheries to electrically insulate the two terminal housing members. A porous separator physically separates the anode and cathode and extends between the terminal housing member peripheries at least partially into the fluid-tight seal. According to one aspect, the separator overlaps the gasket in the seal. According to another aspect, the separator and gasket are formed of a single, integral piece of material.

This patent is a file wrapper continuation application of U.S. patentapplication Ser. No. 08/744,743, filed on Oct. 28, 1996, now abandoned,entitled "Thin Profile Battery With Improved Separator And GasketConstruction" listing the inventors as Peter M. Blonsky and Mark E.Tuttle, which resulted from a divisional application of U.S. patentapplication Ser. No. 08/588,559, filed on Jan. 18, 1996, now U.S. Pat.No. 5,652,070, entitled "Button-Type Battery With Improved Separator AndGasket Construction" listing the inventors as Peter M. Blonsky and MarkE. Tuttle, which resulted from a divisional application of U.S. patentapplication Ser. No. 08/205,611, filed on Mar. 2, 1994, now U.S. Pat.No. 5,547,781, entitled "Button-Type Battery With Improved Separator AndGasket Construction" listing the inventors as Peter M. Blonsky and MarkE. Tuttle.

TECHNICAL FIELD

This invention relates to button-type batteries.

BACKGROUND OF THE INVENTION

Button-type batteries are small thin energy cells that are commonly usedin watches and other electronic devices requiring a thin profile. FIGS.1 and 2 show a conventional button-type battery 20. Battery 20 includesan anode 22, a cathode 24, a porous separator 26 separating the anodeand cathode, and an electrolyte 28 which facilitates ion conductivitybetween the anode and cathode.

These internal battery components are housed within a metal casingformed by a lower conductive can 30 and an upper conductive lid 32. Can30 electrically contacts cathode 24 and thereby forms the positivebattery terminal. Lid 32 electrically contacts anode 22 to form thenegative battery terminal. The can and lid are crimped or pressedtogether to form a fluid-tight seal 34 which entirely encloses theanode, cathode, separator, and electrolyte. An insulating gasket 36 isprovided within primary seal 34 between lid 32 and can 30 toelectrically insulate the two housing members.

There is a need in button-type battery usage to make such energy cellsthinner. Today, the thinnest commercially available button-type batteryhas a thickness of 1.2 mm (47.2 mils). It would be desirable to make athinner battery, particularly one having a thickness of less than 1 mm(39.4 mils). A countering concern, however, is that the integrity of thefluid-tight seal cannot be compromised simply to achieve the goal ofthinner batteries.

Accordingly, it is desirable to design a button-type battery with a verythin profile, yet without degrading the integrity of the fluid-tightseal.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings. The same componentsand features illustrated throughout the drawings are referenced withlike numerals.

FIG. 1 is a top view of a prior art button-type battery.

FIG. 2 is a cross-sectional view taken along line 2--2 in FIG. 1 of theprior art button-type battery.

FIG. 3 is a top view of a button-type battery according to thisinvention.

FIG. 4 is a cross-sectional view taken along line 4--4 in FIG. 3 of thebutton-type battery according to a first preferred embodiment of thisinvention.

FIG. 5 is an enlarged cross-sectional view taken within circle 5 of FIG.4 and shows a C-shaped fluid-tight crimp seal according to thisinvention.

FIG. 6 is a cross-sectional view similar to that view taken along line4--4 in FIG. 3 of a button-type battery according to a second preferredembodiment of this invention.

FIG. 7 is an enlarged cross-sectional view taken within circle 7 of FIG.6 and shows a C-shaped, fluid-tight crimp seal.

FIG. 8 is a top view of a button-type battery according to a third lesspreferred embodiment of this invention.

FIG. 9 is a cross-sectional view taken along line 9--9 in FIG. 8.

FIG. 10 is an enlarged cross-sectional view taken within circle 10 inFIG. 9.

FIG. 11 is a cross-sectional view similar to that taken along line 4--4in FIG. 3 and shows a button-type battery according to a fourth lesspreferred embodiment of this invention.

FIG. 12 is an enlarged cross-sectional view taken in circle 12 of FIG.11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws "to promote the progressof science and useful arts" (Article 1, Section 8).

This invention concerns "coin" or "button-type" batteries. A button-typebattery is typically a small circular-shaped energy cell approximatelythe size of a coin. The button-type battery can be constructed indifferent sizes, with typical diameters being 12 mm, 16 mm, and 20 mm.Other shapes are possible, but the circular shape is most common.

According to one aspect of this invention, a button-type batterycomprises:

an anode;

a cathode positioned adjacent to the anode;

an electrolyte between the anode and the cathode;

a conductive first terminal housing member in electrical contact withone of the anode or the cathode; the first terminal housing memberhaving a periphery;

a conductive second terminal housing member in electrical contact withthe other of the anode or the cathode; the second terminal housingmember having a periphery;

the first and second terminal housing members forming an enclosedhousing which holds and protects the anode and the cathode;

the first and second terminal housing member peripheries beingconfigured together to form a seal which seals the anode and the cathodewithin the housing formed by the first and second terminal housingmembers; and

a separator provided between and separating the anode and the cathode;the separator having a periphery that extends between the first andsecond terminal housing member peripheries at least partially into theseal.

According to another aspect of this invention, a button-type batterycomprises:

an anode;

a cathode positioned adjacent to the anode;

an electrolyte between the anode and the cathode;

a conductive first terminal housing member in electrical contact withone of the anode or the cathode; the first terminal housing memberhaving a periphery;

a conductive second terminal housing member in electrical contact withthe other of the anode or the cathode; the second terminal housingmember having a periphery;

the first and second terminal housing members forming an enclosedhousing which holds and protects the anode and cathode;

an integral separator and gasket layer; the integral layer having (1) acentral portion positioned between the anode and cathode to physicallyseparate the anode and the cathode and to facilitate electrolyticconductivity between the anode and the cathode, and (2) a portionperipheral to the central portion, the peripheral portion beingpositioned between the first and second terminal housing memberperipheries; and

the first and second terminal housing member peripheries and theperipheral portion of the integral separator and gasket layer beingconfigured together to form a fluid-tight seal which seals the anode andcathode within the housing formed by the first and second terminalhousing members, the peripheral portion of the integral layerelectrically insulating the first terminal housing member from thesecond terminal housing member.

Research culminating in the invention disclosed herein also resulted inother inventions. These other inventions are the subject of other U.S.patents which spawned from patent applications filed on the same day ofthe patent application from which this U.S. patent matured. These otherpatent applications are U.S. patent application Ser. No. 08/206,051filed on Mar. 2, 1994. "Method Of Producing Button-Type Batteries AndSpring-Biased Concave Button-Type Battery", listing John R. Tuttle andMark E. Tuttle as inventors (now U.S. Pat. No. 5,486,431); U.S. patentapplication Ser. No. 08/205,590 filed on Mar. 2, 1994, "Methods OfProducing Button-Type Batteries And A Plurality Of Battery TerminalHousing Members", listing Rickie Lake and Peter M. Blonsky as inventors(now U.S. Pat. No. 5,603,157); and U.S. patent application Ser. No.08/205,957 filed on Mar. 2, 1994. "Button-Type Battery Having BendableConstruction, and Angled Button-Type Battery", listing Mark E. Tuttleand Peter M. Blonsky as inventors (now U.S. Pat. No. 5,432,027). Theseco-filed patent applications and resulting patents are herebyincorporated by reference as if fully included herein.

FIGS. 3-5 show a button-type battery 40 according to a first preferredembodiment of this invention. Battery 40 has an anode 42, a cathode 44positioned adjacent to the anode, and a liquid electrolyte 46 betweenthe anode and cathode. Anode 42 and cathode 44 are aligned along atransverse central axis 45.

Button-type battery 40 also includes a circular conductive first, lower,or bottom terminal housing member 48 which forms the can of the energycell. First terminal housing member 48 has a central portion 50 inelectrical contact with cathode 44 and a periphery 52 surroundingcentral portion 50. First housing member 48 defines the positive batteryterminal because it contacts cathode 44.

Battery 40 has a circular conductive second, upper, or top terminalhousing member 54 which forms the lid of the energy cell. The secondterminal housing member 54 has a central portion 56 in electricalcontact with anode 42 and a periphery 58 surrounding central portion 56.By contacting anode 42, second housing member 52 defines the negativebattery terminal. First and second terminal housing members 48 and 54combine to form an enclosed housing 60 which holds and protects anode42, cathode 44, and electrolyte 46. It should be noted that the firstand second terminal housing members 48 and 54 can be alternatelyreversed to electrically contact anode 42 and cathode 44, respectively,thereby reversing their respective terminal polarities.

Anode 42, cathode 44, and electrolyte 46 can be formed of conventionalconstruction. For example, in the reduction to practice models, anode 42comprises elemental lithium provided on a copper backed foil. Anode 42has a preferred thickness of approximately 2 mils (0.0508 mm). Cathode44 is formed of a compressed tablet made from a composite of manganese(IV) oxide, carbon, and teflon powder. Cathode 44 has a preferredthickness of 8 mils (0.2032 mm).

An example electrolyte 36 comprises a solution of propylene carbonateand ethylene glycol dimethylether, having dissolved lithiumtetrafluoroborate. Suitable electrolyte components are supplied byAldrich Chemical Company of Milwaukee, Wis. The volume of electrolyte 46provided within first terminal housing member 48 is preferably gauged tofill the substantial void within housing member 48, yet not so great toleak upon crimp sealing the battery assembly.

First and second terminal housing members 48 and 52 are preferablyformed of a conductive material having a thickness of less than 8 mils(0.2032 mm), with a thickness in a range of approximately 3-5 mils(0.0762-0.1270 mm) being more preferred, and a thickness of 4 mils(0.1016 mm) being most preferred. An example material used for theterminal housing members is Type 304 stainless steel manufactured byTeledyne Rodney Metals of New Bedford, Mass.

An insulating gasket 62 is provided between first and second terminalhousing member peripheries 52 and 58 to electrically insulate firstterminal housing member 48 from second terminal housing member 54.Gasket 62 is preferably formed of an epoxy resin that is screen printedonto can periphery 52 of first terminal housing member 48. Gasket 62 canalternately be deposited onto all three sides 58a, 58b, 58c of lidperiphery 58 of second terminal housing member 54. The gasket can beformed of one or more layers of epoxy resins, with varying degrees ofhardness. An example composite gasket has a harder outer epoxy layeradjacent to battery can periphery 52 and an inner softer epoxy layer.Epoxy gasket material of different resultant hardness are available fromElectronics Materials, Inc., of Brookfield, Conn. Alternately, gasket 62can be formed of other insulative materials, such as polyimide.

First and second terminal housing member peripheries 52 and 58 andinsulating gasket 62 are configured together to form a fluid-tight seal64 which fluidically seals anode 42, cathode 44, and electrolyte 46within housing 60. Seal 64 is preferably a C-shaped crimp seal. Thiscrimp seal is constructed by bending can periphery 52 about lidperiphery 58.

FIG. 5 shows the C-shape crimp seal 64 is more detail. Second terminalhousing member periphery 58 is substantially planar within the seal andprojects substantially radially outward from central axis 45 (i.e.,horizontal in the drawings). First terminal housing member periphery 52and insulating gasket 62 wrap around three sides 58a, 58b, 58c ofbattery lid periphery 58. First terminal housing member periphery 52consists of two substantially planar segments 66 and 68 on respectiveopposing sides 58a and 58c of the substantially planar second terminalhousing member 58 and a continuously bending segment 70 on side 58b oflid periphery 58. Continuously bending segment 70 connects upper segment66 and lower segment 68 and has an example radius of curvature of 3.5mils (0.0889 mm). Most preferably, the planar lid periphery 58 and theplanar upper and lower segments 66 and 68 of can periphery 52 are allsubstantially in parallel.

The action associated with forming C-shape crimp seal 64 produces anindentation in circular first terminal housing member 48. This is causedby the thickness of housing member 48 and the radius of bending segment70 being in combination effectively small to induce compressive stresseswhich result in such upward contraction.

Button-type battery 40 also includes a separator 72 provided betweenanode 42 and cathode 44. Separator 72 includes a central portion 74which physically separates anode 42 and cathode 44 and a peripheralportion 76 surrounding central portion 74. Separator peripheral portion76 extends between the first and second terminal housing memberperipheries 52 and 58 at least partially into seal 64. Moreparticularly, separator periphery 76 is interposed between insulatinggasket 62 and lid periphery 58 to thereby partially overlap withinsulating gasket 62. It should be noted that when gasket 62 isdeposited onto lid periphery 58, separator periphery 76 will beinterposed between insulating gasket 62 and can periphery 52.

Separator 72 is preferably formed of a woven or porous polymericmaterial, such as polyethylene, polypropylene, or teflon. Separator 72has unidirectional pores formed in the Z direction parallel to centralaxis 45 to facilitate electrolytic conductivity between anode 42 andcathode 44. Separator 72 has a preferable thickness of 1 mil (0.0254mm). However, separator periphery 76 is compressed during crimping intoa substantially flat layer having a thickness less than 1 mil (0.0254mm).

Button-type battery 40 of this invention is advantageous over prior artbatteries in that separator 72 extends into the crimped seal 64 toensure complete separation between anode 42 and cathode 44.Additionally, button-type battery 40 has a very thin profile due to thereduced material thicknesses as well as the C-shaped crimp seal 64. Thetotal combined thickness of the anode 42, cathode 44, separator 72, andthe first and second terminal housing members 48 and 54 is less than 1mm, and is most preferably approximately 0.5 mm or less.

FIGS. 6 and 7 illustrate a button-type battery 80 according to a secondpreferred embodiment of this invention. Battery 80 is constructed verysimilar to battery 40 illustrated in FIGS. 4 and 5. The noted differenceis that button-type battery 80 is configured without an insulatinggasket, and instead uses a single, integral separator and gasket layer82. Integral layer 82 has a central portion 84 positioned between anode42 and cathode 44 to physically separate the anode and the cathode.Insulator 82 is porous and thus facilitates electrolytic conductivitybetween the anode and cathode.

Integral layer 82 also has a peripheral portion 86 which surroundscentral portion 84. Peripheral portion 86 is positioned between firstand second terminal housing member peripheries 52 and 58. In thismanner, housing peripheries 52 and 58 and integral layer peripheralportion 86 are configured together to form a fluid-tight seal 88 whichseals the anode, cathode, and electrolyte within the housing. Theperipheral portion 86 thereby electrically insulates the first terminalhousing member 48 from the second terminal housing member 54.Accordingly, integral separator and gasket layer 82 in this secondembodiment serves the dual functions of (1) physically separating theanode and cathode, while promoting electrolytic conductivitytherebetween, and (2) electrically insulating the two housing members.

Integral layer 82 is formed of a porous polymeric material, such as thatdescribed above. The separator may be pre-formed such that the centralportion 84 has a thickness greater than that of the peripheral portion86. Preferably, central portion 84 of integral layer 82 has a thicknessof approximately 1 mil (0.0254 mm) whereas peripheral portion 86 has athickness of approximately 0.5 mil (0.0172 mm). Additionally, peripheralportion 86 of integral separator and gasket layer 82 has a greaterdensity than that of central portion 84. The pre-forming densificationof the peripheral portion can be achieved by heat embossing whicheffectively closes the pores and flattens the polymeric material.Alternatively, the peripheral portion 86 can be densified from thecompression that occurs during the crimping action which forms seal 88.

During assembly, the integral layer is cut in a disk shape and oversizedso that extra material hangs out beyond lid 54. The integral layer isheld in place during the automated assembly operation which crimps firstterminal housing member periphery 52 about second terminal housingmember periphery 58 to form the C-shaped crimp seal. In this manner,peripheral portion 86 of integral layer 82 is folded around all threesides 58a, 58b, and 58c to insure complete electrical insulation betweenhousing member peripheries 52 and 58. Preferably, peripheral portion 86has a peripheral edge 87 that extends exteriorly beyond seal 88 andradially inwardly toward axis 45 on the exterior of battery housing 60.Peripheral edge 87 projects at least partially up along the slopedsection of second terminal housing member 54 (FIG. 7).

Button-type battery 80 is advantageous over prior art batteries in thatintegral separator and gasket layer 82 reduces manufacturing costs andshortens assembly time. Specifically, only a single piece of material isused for both the separating and insulating tasks in the battery cell,as compared to prior art cells which employ two independent components(i.e. both a separator and a gasket). The integral layer thereby reducesmanufacturing costs. Additionally, assembly time is reduced because thethree steps associated with pre-forming a gasket, positioning the gasketwithin the can, and positioning the separator over the cathode arereduced to a single step of positioning the oversized integral layerover the cathode.

FIGS. 8-10 illustrate a button-type battery 90 according to a lesspreferred third embodiment of this invention. Battery 90 differs frombattery 40 illustrated in FIGS. 4 and 5 in the construction of thehousing members. Button-type battery 90 has a substantially planar,disk-shaped first terminal housing member 92. Second terminal housingmember 94 has periphery 96 which is crimped around lid periphery 98 toform a C-shaped crimp seal 100 similar to seal 64 described above indetail. It should also be noted that anode 42 and cathode 44 arereversed so that cathode 44 is electrically contacting second terminalhousing member 92 and anode 42 is electrically contacting secondterminal housing member 94. Separator 72 separates anode 42 and cathode44 and has a periphery 76 that extends radially outward from centralaxis 45 between housing member peripheries 96 and 98 at least partiallyinto C-shaped crimp seal 100.

FIGS. 11 and 12 illustrate a button-type battery 104 according to a lesspreferred fourth embodiment of this invention. Battery 104 is similar tobutton-type battery 40, except that it is designed with a slightlythicker profile. Battery 104 has a first terminal housing member 106which has a central portion 108 that projects from C-shaped crimp seal64 away from second terminal housing member 54 to accommodate a thickeranode 42 and cathode 44. The combined total thickness of anode 42,cathode 44, separator 72, and first and second terminal housing members54, 106 is greater than 20 mils (0.508 mm), as compared to the thinnerprofile button-type battery 40 of FIG. 3, but is still preferably lessthan 40 mils (or approximately 1 mm).

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

We claim:
 1. A circular-shaped thin profile battery defined by a thickness which is less than a maximum linear dimension of its anode, comprising:an anode and a cathode; a conductive first terminal housing member having a periphery and being in electrical contact with one of the anode or the cathode, the conductive first terminal housing member periphery comprising a planar extension; a conductive second terminal housing member having a periphery and being in electrical contact with the other of the anode or the cathode, the conductive second terminal housing member periphery comprising a planar extension parallel to the planar extension of the conductive first terminal housing member periphery; the first and second terminal housing members together forming an enclosed housing which surrounds the anode and cathode; a single undivided separator/gasket, said separator/gasket consisting of only one material; the separator/gasket having (1) a central portion positioned between the anode and cathode to physically separate the anode and the cathode and to facilitate electrolytic conductivity between the anode and the cathode, and (2) a peripheral portion which is peripheral to the central portion, the peripheral portion being positioned between the first and second terminal housing member peripheries; the central portion contacting both the anode and the cathode; the separator/gasket peripheral portion comprising a planar extension which extends along the planar extension of the one of the terminal housing member peripheries and parallel with the planar extensions of both of the terminal housing member peripheries, the separator/gasket physically contacting only one of the terminal housing members; the planar extension of the separator/gasket being between the planar extensions of the terminal housing member peripheries; the planar extensions of the first and second terminal housing member peripheries and the planar extension of the peripheral portion of the separator/gasket together forming a fluid-tight seal; and wherein; the separator/gasket is formed of a porous material; the central portion has a first thickness and a first density; and the peripheral portion has a second thickness less than the first thickness and a second density greater than the first density.
 2. The circular-shaped thin profile battery of claim 1 wherein the terminal housing member in physical contact with the separator/gasket is the same terminal housing member that is in electrical contact with the anode. 